Sealing glass parts to form cathode ray tube envelopes



May 30, 1967 A. c. Mr-:xREsoNNE 3,322,522

SEALING GLASS PARTS TO FORM CATHODE RAY TUBE ENVELOPES original FiledFeb. 11, 196s 5 Sheets-sheet. 2

FICLZ y" l 16 May 30, 1967 A. c. MEIREsoNNE 3,322,522

SEALING GLASS PARTS TO FORM CATHODE RAY TUBE ENVELOPES Original FiledFeb. ll, 1963 5 Sheets-Sheet 5 FIG. 9

United States Patent tiP 3,322,522 Patented May 30, 1967 3,322,522SEALING GLASS PARTS T() FORM CATHGDE RAY TUBE ENVELOIES Arthur C.Meiresonne, Columbus, Ohio, assigner to Owens-illinois, Ene., acorporation of Ghio Continuation of application Ser. No. 257,458, Feb.11,

1963. This application Aug. 24, 1966, Ser. No. 579,443

8 Claims. (Cl. (iS-40) This application is a continuation of mycopending application Ser. No. 257,458, filed Feb. 11, 1963, nowabandoned.

This invention relates to sealing hollow glass parts to form cathode raytube envelopes and the like.

In the manufacture of glass envelopes for use in electronic tubes suchas television tubes and cathode ray tubes of other types, it isconventional to join a hollow glass funnel and a hollow glass faceplate. The funnel is conventionally made by centrifugal casting and asealing edge is formed on the large end of the frusto-conical portion ofthe funnel by scoring the heated funnel and causing a portion of the endof the funnel to ring off to define the sealing edge on the funnel. Theface plate is -conventionally made by pressing a charge of glass to forma face plate portion and an annular peripheral flange portion which hasa sealing edge defining a substantially ilat planar surface. The partsare conventionally joined to one another by placing in a lathe andapplying heat to the sealing edges. As soon .as the parts are hot enoughto show red color, electrical current is introduced to facilitateheating and after proper heating, the parts are brought together whilecontinuing the heating.

Because the sealing edge on the funnel is made by ringing off, gl-as-sirregularities are found in the sealing edge and it is necessary tothermally shock the sealing edge of the funnel by apply-ing heat toremove these glass irregularities. Thus, the sealing edge of the funnel,which is also usually thinner than the edge of `the face plate, has moreheat applied thereto and it is difficult to subsequently heat thesealing edge of the face plate suiciently to provide a complete andsatisfactory joint.

It is therefore an object of this invention to provide a face platehaving a novel sealing edge design which facilitates the thermal fusionof the face plate to the funnel.

It is a further object of the invention to provide such a face platewhich facilitates the heating of the sealing edges of the face plate`and permits a more efficient heating of the sealing edge.

It is a further object of the invention to provide -an improved jointbetween the funnel and face plate.

Basically, the invention comprises forming the flange portion of theface plate such that the sealing edge has the major portion thereoflying on the radially innermost side of the `.axial center line of thecross section of the flange portion. This results in la small volume tosurface ratio `at the sealing edge so that the heating rate of thesealing edge will occur more rapidly. Since the major portion of thesealing edge is in the innermost side of the axial center line of thecross section of the flange portion and has a small volume to surfaceratio, this edge will initially heat faster, thus taking and conductingthe electrical current more readily resulting in heating the sealingedge in a line which is on the innermost side of the axial center lineof the cross section of the flange as compared to heating from the outersurface with the conventional design. This provides a better and moreeicient hermetic` joint between the parts.

In the drawings:

FIG. 1 is a fragmentary sectional View through a molding apparatus forforming the face plate.

l FIG. 2 is a plan view of a face plate embodying the invention.

FIG. 3 is a fragmentary sectional view on an enlarged scale taken alongthe line 3 3 in FIG. 2.

FIG. 4 is a fragmentary sectional view on an enlarged scale taken alongthe line 4 4 in FIG. 2.

FIG. 5 is a fragmentary sectional view on an enlarged scale taken alongthe line 5-5 in FIG. 2.

FIG. 6 is a partly diagrammatic sectional View showing the relativeposition lof the funnel and face plate during an initial stage in thesealing of the funnel and the face plate.

FIG. 7 is a view similar to FIG. 6 showing the relative positions of theparts during a further stage in the sealing thereof.

FIG. `8 is a sectional View showing the final joint between the parts.

FIG. 9 is an elevational view of a cathode ray tube envelope after thefunnel and face plate have been joined.

Referring to FIG. 1, the face plate 10 embodying the invention is madein a conventional apparatus by pressing a charge of glass. Suchapparatus includes a mold `11 into which the charge of glass is placed,a removable ring 12 and a plunger 13 w-hich is pressed downwardly intothe charge of glass and cooperates with the mold 11 and ring 12 to formthe charge into the desired shape. The plunger 1-3 is formed with aninterior liquid distributor 14 which provides liquid to cool theinterior surface 1S of the mold. The plunger and distributor are mountedon a ram 16.

In accordance with the invention, the interior surface 17 of the ring 12is shaped to provide a specific con- Ifiguration to the flange 18 of theface plate 10. The flange 18 comprises a peripheral wall that extendsaround the face plate portion 19 of the face plate 10.

As shown in FIGS. 3, 4 and 5, the surface 17 is shaped so that theexterior surface of the iiange portion 1S includes a first portion 2li1tapering slightly inwardly toward the edge of the ilange portion 18, asecond portion 21 tapering inwardly at a slightly greater angle and asealing edge 22 comprising a bead which is arcuate in cross section anda short ledge 23 which is needed to provide strength to the portion 24of the ring 12.

The surfaces 20, 21 are so positioned with respect to the cross sectionof the flange 18 that the center R of the radius of the bead 22 and, inturn, the major portion of the bead 22 lies radially inwardly of anaxial center line C through the cross section 18. Axial center line C isdrawn by connecting the centers of the flange cross section between themold seam, formed by the mold 11 and ring 12, and the area which isdistorted in the sealing process. In other words, the cross section ofthe flange portion 1S is unsymmetrical adjacent the sealing edge withthe greater portion of the sealing edge lying radially inwardly of theaxial center line through the cross section of the flange portion.

When a flame is applied to the sealing edge, as presently described, thesealing edge will be more readily heated and therefore will reach atemperature such that current will pass therethrough sooner. Thispermits a better balance of the timing 0f the heating of the funnel edgeand the face plate edge so that a better joint is achieved between theface plate and funnel.

Referring to FIGS. 6 8, the funnel 25 comprises a frusto-conical portionwhich has a sealing edge 26 at the larger end thereof. The sealing edge26 is conventionally formed in the funnel by grooving and annularlyscoring the funnel after the funnel has been centrifugally cast from acharge of glass and permitting a ring or moil of glass to be broken offof the funnel due to an annular pattern of fracture sources which resultin moil separation when the funnel is cooled. The resultant sealing edgeLr 26 is often formed with irregularities that must be removed bythermally shocking the edge of the funnel by application of a flame F(FIG. 6).

The sealing operation is then continued by application of an additionalflame F on the flange portion of the face plate. Conventionally, thesecond flame F is not applied to the edge of the face plate until theflame F has heated the sealing edge 26 sufficiently to removeirregularities.

After the heating of the sealing edge of the face plate has beeninitiated and the parts are heated to a red heat, they are forcedtogether axially as shown in FlG. 7 and an electric current is appliedas by passage through the gaseous flame.

The provision of the sealing edge 22 of the face plate radially inwardlyof the major portion of the cross section of the flange 18 of the faceplate permits the flame F to heat the sealing edge more completely andmore rapidly so that when the parts are brought together, that part ofthe sealing edge which is at the highest temperature is radially inwardof the major portion of the cross section thus giving the inner surfaceof the seal added strength. In addition, the higher temperature of thesealing edge 22 will permit the electrical current to flow through thesealing edge 22 and as well as the sealing edge 26 and facilitate theformation of a better joint.

The provision of the tapered surface 21 on the flange po1lion 1S permitsthe flame F to be applied at a right angle to the surface 21 furtherfacilitating the heating of the sealing edge. This may be contrasted toprior art constructions wherein the flame F' was conventionally appliedalong a radial direction.

The flnal joint as shown diagrammatically in FIG. l8 provides for a morecomplete and thorough fusion and is therefore a more perfect hermeticseal between the parts (FIG. 9).

I claim:

1. The method of thermally fusing two hollow glass parts which comprisespositioning said parts with annular wall portions thereof in juxtaposedoverlapping relation,

each said part having a sealing edge on the wall portion thereof,

the cross-sectional area of the sealing edge of the wall portion of saidsecond part being unsymmetrical such that the major portion of the areathereof lies radially inwardly of a center line extending axiallythrough the cross section of the wall portion,

heating the sealing edges of the two parts by application of flamethereto,

forcing the heated sealing edges of the two parts together axially,

continuing the application of heat by flame and simultaneously applyingan electric current into the heated edges.

2. The method of thermally fusing two hollow glass parts which comprisespositioning said parts with annular wall portions thereof in juxtaposedoverlapping relation,

one of said parts having an edge formed by scoring and ringing off amoil portion,

applying a flame to the edge of said one part to remove irregularitiesin the edge thereof,

the other said part having the cross-sectional area of the sealing edgethereof such that the major portion of the area thereof lies radiallyinwardly of a center line extending axially through the cross section ofthe wall portion,

thereafter applying heat by flame to the sealing edge of the other saidpart to heat said edge,

forcing said heated edges of said parts together axially,

continuing the application of heat by llame and simultaneously applyingan electric current to the heated edges.

3. The method of thermally fusing two hollow glass parts, one said partcomprising a viewing portion and a peripheral flange portion extendingaxially away from the viewing portion, said flange portion having anannular sealing edge defining a substantially planar sealing surface,the other said part comprising a funnel,

the method which comprises positioning said parts with the edges thereofin juxtaposed overlapping relation, said funnel having the edge formedby scoring and ringing off a moil portion,

applying a flame to the edge of said funnel to remove irregularities inthe edge thereof,

the cross-sectional area of the sealing edge of the flange portion ofsaid one part being unsymmetrical such that the major portion thereoflies radially inwardly of a center line extending axially through thecross section of the flange portion,

thereafter applying heat by flame to the sealing edge of the flangeportion to seat said edge,

forcing said parts together axially,

continuing the application of heat by flame and simultaneously applyingan electric current to the heated edges.

4. The method set forth in claim 3 wherein the flange portion of saidpart includes an outer surface tapering inwardly toward the sealingedge, said flame being directed against said sealing edge atsubstantially a right angle to said tapered surface.

5. The method set forth in claim 3 wherein said sealing edge of said onepart includes a continuous peripheral bead thereon, substantially theentire cross section of said bead lying radially inwardly of said centerline of the cross section of said flange portion, said flame beingdirected against said bead.

6. The method set forth in claim 3 wherein the flange portion of saidpart includes an outer surface tapering inwardly toward the sealingedge, said flame being directed against said sealing edge atsubstantially a right angle to said tapered surface, said sealing edgeof said one part including a continuous peripheral bead thereon,substantially the entire cross section of said bead lying radiallyinwardly of said center line of the cross section of said flangeportion, said flame being directed against said bead.

7. A method as claimed in claim 1 wherein the edges of said parts arealso heated by an electric current prior to, during and after forcingsaid parts axially together.

8. A method as claimed in claim 3 wherein the edges of said parts arealso heated by lan electric current prior to, during and after forcingsaid parts axially together.

References Cited UNITED STATES PATENTS 2,006,818 7/1935 Zimber 65-155 X2,306,054 12/1942 Guyer 65-40 2,959,894 11/1960 Zonneveld 65-40 FOREIGNPATENTS 229,103 4/ 1959 Australia. 404,465 1/ 1937 Great Britain.

S. LEON BASHORE, Acting Primary Examiner.

R. L. LNDSAY, Assistant Examiner.

1. THE METHOD OF THERMALLY FUSING TWO HOLLOW GLASS PARTS WHICH COMPRISESPOSITIONING SAID PARTS WITH ANNULAR WALL PORTIONS THEREOF IN JUXTAPOSEDOVERLAPPING RELATION, EACH SAID PART HAVING A SEALING EDGE ON THE WALLPORTION THEREOF, THE CROSS-SECTIONAL AREAD OF THE SEALING EDGE OF THEWALL PORTION OF SAID SECOND PART BEIG UNSYMMETRICAL SUCH THAT THE MAJORPORTION OF THE AREA THEREOF LIES RADIALLY INWARDLY OF A CENTER LINEEXTENDING AXIALLY THROUGH THE CROSS SECTION OF THE WALL PORTION, HEATINGTHE SEALING EDGES OF THE TWO PARTS BY APPLICATION OF FLAME THERETO,FORCING THE HEATED SEALING EDGES OF THE TWO PARTS TOGETHER AXIALLY,CONTINUING THE APPLICATION OF HEAT BY FLAME AND SIMULTANEOUSLY APPLYINGAN ELECTRIC CURRENT INTO THE HEATED EDGES.